1. Field of the Invention
The present invention relates to a variable wavelength generating method and an apparatus thereof, for use in measuring body fluid constituent concentration, and more particularly, to a variable wavelength generating method and an apparatus thereof, capable of generating a wavelength of a specific wavelength band in an easy and convenient manner in order to measure a body fluid constituent concentration.
2. Description of Related Art
Recently, as living environments are remarkably improved and life conditions are promoted, interest in individual health is being stressed. Accordingly, lots of research for developing medical implements for home use capable of easily monitoring a health status of an individual several times a day have been carried out and new products are being developed continuously.
In healthy people, body fluid existing inside of the living body is circulated and adjusted organically so that an amount of the body fluid is maintained within in a predetermined range. Examples of such body fluid include blood, urine, interstitial fluid, sweat, and saliva. Particularly, a concentration of a constituent within the body fluid, such as blood, urine (sugar, protein) is a very important variable informing a health status of an individual. Further, a concentration measurement for glucose, hemoglobin, bilirubin, cholesterol, albumin, creatinine, protein, urea existing in an inside of the body fluid is an important object.
However, if the living body gets an illness, a change is generated in a composition or an amount of a body fluid constituent and a dangerous condition may be caused. For example, a blood glucose's concentration of a healthy person is about 80 mg/dl before a meal and 120 mg/dl after a meal. To maintain the blood glucose's concentration, the living body has the pancreas secret an appropriate amount of insulin before and after a meal so that the insulin may be absorbed in the liver and a skeletal muscle cell. However, in case the insulin necessary for maintaining a normal blood glucose is not produced from the pancreas due to a disease or other reason, an excessive amount of glucose gets remained in an inside of blood. Such an excessive glucose remaining in blood may cause a disease in the heart and the liver, arteriosclerosis, high blood pressure, cataract, retinal hemorrhage, nerve injury, hearing loss, and sight deterioration. In a severe case, it may cause a death.
Therefore, it is important to measure a change in the body fluid constituent in an inside of the living body before such an adverse result is caused. For a concentration measurement method for a body fluid constituent, an invasive method for measuring a concentration of a body fluid constituent by directly extracting part of a subject matter and a non-invasive method for performing a measurement without extracting the subject matter. However, since there are lots of problems in the invasive method, a technology for easily diagnosing the body fluid constituent in a non-invasive manner has been being developed. A conventian process for the measurement for a blood glucose has been performed in the following way that blood is extracted to react to a reagent so that results thereof may be used for a clinical analysis or a color change of a test strip that has reacted to a reagent is quantified and used in a diagnosis. When such invasive blood extractions are performed everyday, a painful burden is given to a diabetic and possibility of infection to a disease is increased. Further, since continuous monitoring is hard to perform, it is difficult to take an appropriate measure upon emergence situations. When a strip and a reagent, a great amount of consumables should be used, which gives a burden to a user economically. Further, since the consumables are environment-polluting materials, they should be processed in someway or another. Accordingly, a technology for diagnosing a blood glucose concentration without extracting blood not using a strip or a consumable in order to adjust blood glucose of a diabetic or to perform a medical examination of a healthy people, is highly required.
Spectroscopic methods for use in measuring a concentration of the body fluid constituent within the living body, are mostly a method of illuminating visible light or light of a near infrared (NIR) wavelength region onto part of a living tissue and detecting the light reflected or transmitted therefrom. That is, the method estimates a concentration of the body fluid constituent by mainly measuring its spectrum. For estimation of a specific target constituent concentration, a reference light source of a wavelength band for effectively canceling influence of interfering materials as well as a light source of a wavelength for most readily responding to the constituent to be measured is required.
In the conventional art, a concentration has been computed by measuring a light intensity with an array-type light detector, which is high priced, using a continuous wavelength (CW) lamp light source or by measuring a spectrum with a spectrometer, or a plurality of light emitting diodes (LED) or laser diodes (LD) for generating a specific wavelength have been used.
Since the concentration of the constituent to be measured is very low in blood among the body fluids and a scattering effect of light is very larger than an absorption effect in a biologic tissue and blood, a detected signal is weak, thus a method for amplifying the detected signal is required. Amplification of the detected signal can be achieved by a pulse driving rather than a CW driving of an LD. Since organic matter existing within one living body is constantly flowing, a measurement time should be maintained fast so as to exactly measure a concentration of an organic matter constituent.
Simultaneously, it should be considered that the overall average energy illuminated onto a human body may not exceed a range that causes a damage to a human tissue. Particularly, since an absorption band for glucose is widely distributed in an NIR region ranging from 700 nm to 2500 nm, a glucose absorption peak is relatively small compared to a big aqueous background spectrum, and a small S/N (signal-to-noise ratio) value is shown, exact measurement of a concentration is hard to perform.
The U.S. Pat. No. 5,086,229 entitled “Non-invasive measurement of blood glucose” suggests a method of measuring a glucose concentration within blood in a non-invasive manner, in which: wavelengths of from 600 nm to 1100 nm are used, such wavelengths are obtained using a variety of LEDs, and an energy difference of light transmitted or reflected from a living body is analyzed so that the glucose concentration can be estimated. However, since a great number of LEDs should be combined and used for obtaining a sufficiently strong signal in a glucose absorption wavelength region actually suggested, there is a problem that alignment of LEDs having different wavelengths is not easy. Further, since LEDs having different wavelengths are combined and used, each wavelength is not illuminated onto the same position upon illumination onto a biologic tissue, and thus exact concentration measurement is hard to perform. Still further, there is a problem that the region of from 600 nm to 1100 nm does not include useful glucose information.
The U.S. Pat. No. 6,040,578 entitled “Method and apparatus for multi-spectral analysis of organic blood analytes in noninvasive infrared spectroscopy” relates to an apparatus and a method for measuring a concentration of various blood constituent existing within a living body using a wavelength of from 1100 nm to 5000 nm. Since the above-suggested method detects and analyzes the only light reflected from the living body, a variety of filters is used or a linear array detector is used. However, such a spectrometer, a grating, and an optical element such as a mirror should be used. Accordingly, there exist a fundamental limitation in manufacturing a small-sized product.
The U.S. Pat. No. 5,780,867 entitled “Broadband light-emitting diode” suggests a method for obtaining results by manufacturing III-V group compound semiconductor layers having various energy band-gap in order to generate wide-band wavelengths of from 1.3 μm to 2 μm. However, since a separate spectrometer of a spectroscopic type is additionally required for development of a wavelength variable light source, the commercialized spectrometer of the conventional art can only be used.